How many atoms are in 0.551 g of potassiom?

Answer 1

Seems to me we need to convert grams to atoms. So lets use mole conversion. When you convert from grams to moles, you divide the gram amount by the molar mass(a.k.a. Atomic Mass). So go look at a Periodic Table of elements and you'll see that pottasium's atomic mass is about 39.1 amu. So:

.551/39.1 = .0141 mol

Now that you have moles, you convert to particles(atoms). When converting from moles to anything you multiply. When converting from moles to particles you multiply by Avogadro's number(6.022 x 10^23). So:

6.022 x 10^23 x .0141 = about 8.49 x 10^21 atoms.